This invention relates to antennas for portable radios, particularly miniature radios of the type having a molded plastic housing which is partly electrically conductive to also serve as the radio antenna.
A prior art radio set of this general type, as disclosed, for example, in U.S. Pat. No. 3,736,591, has included a compound housing structure comprising a box-like molded plastic casing and a U-shaped metallic cover slidably fitted thereover via groove means to serve as a receiving antenna. Such a housing structure is disadvantageous in that the casing box inside the metallic cover is limited to its volumetric capacity to accommodate the radio circuitry components in view of the external dimensions of the cover, and this acts against miniaturization and portability. To increase the internal volume of the housing structure the roundness of the edges or corners of the housing must be reduced on both the outside and inside, and such increased angularity of the housing corners is more likely to tear the pocket of the users suit in which the radio is inserted and carried.
Further, with a speaker device mounted in the housing the thin metallic cover is liable to vibrate in sympathetic resonance with the speaker, thus producing undesirable and annoying acoustic effects. In addition, when the radio is hand held at a low temperature, e.g., -10.degree. C., it may become difficult to release the cold metallic cover of the housing due to skin moisture freezing.